The present invention relates to cooling apparatus for an enclosed space using outdoor air as a cooling medium during cold weather. Although not so limited, the apparatus of the invention has particular utility in controlling temperature in dairy and produce cases, beverage and meat coolers and the like in supermarkets, meat cutting rooms, food processing and storage facilities, and similar enclosures wherein temperatures may require maintenance within a range of 20.degree. to 55.degree. F.
During winter months when outside air temperatures are below the required controlled temperature within an enclosed space of the type described above, the use of the apparatus of the invention permits deactivation of mechanical refrigeration systems with substantial savings in electrical energy. Calculations made by applicant indicate that the apparatus of the present invention would pay for itself within two to three months, based on a cost of 12 cents to 15 cents per kilowatt hour for electricity.
The use of ambient air for supplementary cooling has been proposed previously. However, none of the systems of which applicant is aware offers economy of operation and low installation cost comparable to the apparatus of the present invention.
U.S. Pat. No. 4,244,193 discloses a cooling system which includes a conventional mechanical refrigeration system and a first thermostat operative to actuate the refrigeration system at a predetermined upper temperature and to deactivate the system at a predetermined intermediate temperature; air flow passage means connecting the interior of an enclosure with the outdoors; fan means to draw ambient air into the enclosure through the air flow passage means; a second thermostat responsive to the temperature within the enclosure and operative to activate the fan means at the intermediate temperature and to deactivate the fan means at a predetermined low temperature below the intermediate temperature; and an outdoor temperature sensor responsive to ambient air temperature and operative to energize the second thermostat and render it operative to activate the fan means at a predetermined ambient temperature less than the intermediate temperature. Motorized damper means are positioned in the air flow passage means, the motorized damper means being connected in a control circuit with the second thermostat for actuation to an open position at the intermediate temperature level and for movement to a closed position at the low temperature level. An exhaust opening is also provided with motorized exhaust damper means, also connected in the control circuit with the second thermostat for actuation in the same manner as the motorized damper means positioned in the air flow passage means.
U.S. Pat. No. 4,250,716 discloses apparatus for use with conventional refrigeration systems, utilizing ambient air during cold weather. This system comprises a rectangular housing mounted within the space to be cooled having an end wall and side walls, an atmospheric air inlet in one of the housing walls, an atmospheric air outlet in another wall, a fan within the housing having an inlet port communicating with the air inlet and an outlet port communicating with the air outlet, an electric motor connected to the fan, first temperature sensing means mounted upon the housing sensing the temperature of the air within the space to be cooled, second temperature sensing means sensing atmospheric air temperature, control means on the housing electrically connected to the motor and first and second temperature sensing means adapted to energize the motor when the first sensing means indicates the need for cooling and when the second sensing means senses a predetermined atmosphereic temperature. The first temperature sensing means includes a first sensing bulb, and the second temperature sensing means is mounted within the housing and includes a second sensing bulb located within the atmospheric air inlet of the housing.
U.S. Pat. No. 4,358,934 discloses apparatus for utilizing atmospheric air to cool enclosures comprising a panel mounted upon the inner surface of the enclosure, an atmospheric air inlet in the panel, an enclosure air exhaust outlet in the panel, an exhaust fan mounted on the panel for direct communication with the enclosure for selectively exhausting air through the exhaust outlet, a first air duct having an end in alignment with and communicating with the panel inlet and a second end communicating with atmospheric air, an atmospheric air supply fan having an outlet in communication with the first air duct at the second end, a second air duct having a first end in alignment with and communicating with the exhaust outlet and a second end in communication with atmospheric air, and air temperature responsive fan control means electrically connected to the air supply and exhaust fans sensing the enclosure and atmospheric air temperatures so as to simultaneously energize the fans at predetermined enclosure and atmospheric temperature conditions. The fan control means is mounted on the panel intermediate the panel air inlet and exhaust outlet. This arrangement is not interconnected with a mechanical refrigeration system.
Despite the prior art systems disclosed in the above and earlier patents referenced therein, there is still a genuine need for a reliable, simplified air cooling system which can be inexpensively and easily connected to existing or new installations and which achieves substantial energy savings.